Platform margin belt structure and sedimentation characteristics of Changxing Formation reefs on both sides of the Kaijiang-Liangping trough, eastern Sichuan Basin, China

This article discusses the types and characteristics of platform margin belts on both sides of the Kaijiang-Liangping trough in the Sichuan Basin during the Late-Permian Changhsingian age combined with the seismic reflection characteristics. The results show that there are four types of platform margin belts on both sides of the Kaijiang-Liangping trough: (1) steep-slope, single-platform margin belts controlled by faults; (2) steep-slope, single-platform margin belts controlled by paleogeomorphology; (3) steep-slope, multiple-platform margin belts controlled by paleogeomorphology; and (4) gentle-slope, multiple-platform margin belts controlled by paleogeomorphology. Reefs developed in the different types of platform margin belts exhibit different morphological characteristics and stacking patterns. Among all the reefs that developed in steep-slope, platform marginal belts are mainly characterized by aggradational accretion and different degrees of lateral migration in different directions. In contrast, the reefs developed in gentle-slope platform margin belts show distinctive characteristics of multiple bandings and lateral extension. Research suggests that the differences in the platform margin belts’ structure and reefs’ development rules are jointly controlled by a combination of syn-sedimentary fault activities, paleogeomorphology, and sea-level fluctuations. These results can be used to explore and predict reef reservoirs on carbonate platform margins.